Hybrid adaptive lenses for head-mounted displays

ABSTRACT

A hybrid lens includes a transmissive adaptive liquid lens and an optical element including liquid crystals. The adaptive liquid lens includes a layer of optical fluid on a substrate. A focal length of the adaptive liquid lens is adjustable. The optical element including liquid crystals is optically coupled with the adaptive liquid lens. The optical element including liquid crystals is configured to adjust a refractive index across the optical element including liquid crystals in conjunction with adjusting the focal length of the adaptive liquid lens so that the optical element reduces optical artifacts caused by the adaptive liquid lens.

RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/873,765, filed Jan. 17, 2018, entitled “HybridAdaptive Lenses for Head-Mounted Displays,” which is incorporated byreference in its entirety.

TECHNICAL FIELD

This relates generally to lenses, and more specifically to adaptivelenses used in head-mounted display devices.

BACKGROUND

Head-mounted display devices (also called herein head-mounted displays)are gaining popularity as a means for providing visual information to auser.

Virtual reality head-mounted displays simulate virtual environments andaugmented reality head-mounted displays present virtual imagesoverlapping with a real world view. Both systems require stereoscopicimages displayed on a display of a head-mounted device to illustrate anillusion of depth. Displaying such images requires varifocal opticalelements.

SUMMARY

There is a need for varifocal optical elements for virtual and augmentedreality head-mounted devices that adjust focus of light emitted by thedisplay device such that it appears at a particular focal distance. Theoptical elements are required to adjust the focal distance very fast andproduce images with high optical quality, thereby enhancing the user'svirtual reality and/or augmented reality experience.

Adaptive liquid lenses have a number of properties that make themdesirable candidates for varifocal elements of head-mounted displaydevices. Such properties include a large aperture, light weight, largeoptical power, high image quality and fast adjustment of a focaldistance. However, adaptive liquid lenses suffer from a number ofchallenges that limit their use in head-mounted displays. For example,liquid lenses are susceptible to a gravity effect (e.g., when positionedin a vertical orientation), a temperature effect, and/or, over time, acreep effect.

The above deficiencies and other problems associated with liquid lensesare reduced or eliminated by the hybrid adaptive lenses describedherein. In some embodiments, the hybrid adaptive lenses are included ina display device. In some embodiments, the device is a head-mounteddisplay device. In some embodiments, the device is portable.

In accordance with some embodiments, a method includes adjusting a focallength of an adaptive liquid lens that includes a layer of optical fluidon a substrate, and in conjunction with adjusting the focal length ofthe adaptive liquid lens, adjusting a liquid crystal element coupledwith the adaptive liquid lens. The method also includes transmittinglight through the adaptive liquid lens and the liquid crystal element.

In accordance with some embodiments, a hybrid lens includes an adaptiveliquid lens and a liquid crystal element coupled with the adaptiveliquid lens. The adaptive liquid lens includes a layer of optical fluidon a substrate, where a focal length of the adaptive liquid lens isadjustable.

In accordance with some embodiments, a head-mounted display deviceincludes a hybrid lens described herein.

Thus, the described hybrid lenses of the present disclosure provideoptical elements including an adaptive liquid lens with reduced opticalartifacts.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the various described embodiments,reference should be made to the Description of Embodiments below, inconjunction with the following drawings in which like reference numeralsrefer to corresponding parts throughout the figures.

FIG. 1 is a perspective view of a display device in accordance with someembodiments.

FIG. 2 is a block diagram of a system including a display device inaccordance with some embodiments.

FIG. 3 is an isometric view of a display device in accordance with someembodiments.

FIG. 4A is a schematic illustration of a gravity effect of liquid lensesin accordance with some embodiments.

FIG. 4B is a graph illustration of a creep effect in liquid membranelenses in accordance with some embodiments.

FIG. 5A is a schematic illustration of an adaptive liquid lens inaccordance with some embodiments.

FIG. 5B is a schematic illustration of a hybrid adaptive lens inaccordance with some embodiments.

FIG. 5C is a schematic illustration of a hybrid adaptive lens inaccordance with some embodiments.

FIG. 6A is a schematic illustration of an adaptive liquid lens inaccordance with some embodiments.

FIG. 6B is a schematic illustration of a dielectrophoretic lens inaccordance with some embodiments.

FIG. 6C-6D are schematic illustrations of a membrane lens in accordancewith some embodiments.

FIG. 7 is a schematic illustration of a liquid crystal wave-frontcorrector in accordance with some embodiments.

These figures are not drawn to scale unless indicated otherwise.

DETAILED DESCRIPTION

Head-mounted display devices require varifocal optical elements that arecapable of adjusting a focal distance of light for displayingstereoscopic computer-generated virtual and/or augmented reality images.For example, augmented reality head-mounted display devices requirevarifocal optical elements for displaying virtual images overlappingwith a real world view at a specific distance for an eye of a user toaccommodate when focusing on objects at different depths. Virtualreality head-mounted display devices require varifocal optical elementsfor correctly rendering or otherwise compensating forvergence-accommodation conflicts. Varifocal optical elements forresolving vergence-accommodation conflicts in virtual and/or augmentedreality head-mounted devices are described in U.S. Patent ApplicationNo. 62,372,387, titled “Focus Adjusting Liquid Crystal Lenses in aHead-Mounted Display,” filed Aug. 9, 2016, the contents of which areherein incorporated by reference in their entirety.

Adaptive liquid lenses have a number of desirable properties forvarifocal optical elements of head-mounted display devices. For example,liquid lenses provide high quality images without haze, and have a largeaperture size (e.g., equal to or larger than 4 cm), large optical power(±2D), and fast adjustment of focus (e.g., an adjustment speed of lessthan 300 ms). Liquid lenses, especially liquid lenses with a largeaperture size, are susceptible to optical artifacts caused bytemperature fluctuations, gravity and/or, over time, a creep effect thatlimit the use of liquid lenses in head-mounted display devices. Liquidlenses can be heavy and thick compared to liquid crystal lenses. Suchchallenges and other problems associated with liquid lenses are reducedor eliminated by the hybrid adaptive lenses described herein.

Reference will now be made to embodiments, examples of which areillustrated in the accompanying drawings. In the following description,numerous specific details are set forth in order to provide anunderstanding of the various described embodiments. However, it will beapparent to one of ordinary skill in the art that the various describedembodiments may be practiced without these specific details. In otherinstances, well-known methods, procedures, components, circuits, andnetworks have not been described in detail so as not to unnecessarilyobscure aspects of the embodiments.

It will also be understood that, although the terms first, second, etc.are, in some instances, used herein to describe various elements, theseelements should not be limited by these terms. These terms are used onlyto distinguish one element from another. For example, a first lens couldbe termed a second lens, and, similarly, a second lens could be termed afirst lens, without departing from the scope of the various describedembodiments. The first lens and the second lens are both lenses, butthey are not the same lens.

The terminology used in the description of the various describedembodiments herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used in thedescription of the various described embodiments and the appendedclaims, the singular forms “a,” “an,” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will also be understood that the term “and/or” as usedherein refers to and encompasses any and all possible combinations ofone or more of the associated listed items. It will be furtherunderstood that the terms “includes,” “including,” “comprises,” and/or“comprising,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof. The term “exemplary” is used herein in the senseof “serving as an example, instance, or illustration” and not in thesense of “representing the best of its kind.”

FIG. 1 illustrates display device 100 in accordance with someembodiments. In some embodiments, display device 100 is configured to beworn on the head of a user (e.g., by having the form of spectacles oreyeglasses, as shown in FIG. 1) or to be included as part of a helmetthat is to be worn by the user. When display device 100 is configured tobe worn on the head of a user or to be included as part of a helmet,display device 100 is called a head-mounted display. Alternatively,display device 100 is configured for placement in proximity to an eye oreyes of the user at a fixed location, without being head-mounted (e.g.,display device 100 can be mounted in a vehicle, such as a car or anairplane, for placement in front of an eye or the eyes of the user).

In some embodiments, display device 100 includes one or more componentsdescribed below with respect to FIG. 2. In some embodiments, displaydevice 100 includes additional components not shown in FIG. 2.

FIG. 2 is a block diagram of system 200 in accordance with someembodiments. The system 200 shown in FIG. 2 includes display device 205(which corresponds to display device 100 shown in FIG. 1), imagingdevice 235, and input interface 240 which are each coupled to console210. While FIG. 2 shows an example of system 200 including one displaydevice 205, imaging device 235, and input interface 240, in otherembodiments, any number of these components may be included in system200. For example, there may be multiple display devices 205 each havingassociated input interface 240 and being monitored by one or moreimaging devices 235, with each display device 205, input interface 240,and imaging device 235 communicating with console 210. In alternativeconfigurations, different and/or additional components may be includedin system 200. For example, in some embodiments, console 210 isconnected via a network (e.g., the Internet) to system 200 or isself-contained as part of display device 205 (e.g., physically locatedinside display device 205). In some embodiments, display device 205 isused to create mixed reality by adding in or allowing in a view of thereal surroundings. Thus, display device 205 and system 200 describedhere can deliver virtual reality, mixed reality, and augmented reality.

In some embodiments, as shown in FIG. 1, display device 205 is ahead-mounted display that presents media to a user. Examples of mediapresented by display device 205 include one or more images, video,audio, or some combination thereof. In some embodiments, audio ispresented via an external device (e.g., speakers and/or headphones) thatreceives audio information from display device 205, console 210, orboth, and presents audio data based on the audio information. In someembodiments, display device 205 immerses a user in a virtualenvironment.

In some embodiments, display device 205 also acts as an augmentedreality (AR) headset. In these embodiments, display device 205 augmentsviews of a physical, real-world environment with computer-generatedelements (e.g., images, video, sound, etc.). Moreover, in someembodiments, display device 205 is able to cycle between different typesof operation. Thus, display device 205 may operate as a virtual reality(VR) device, an AR device, as glasses or as some combination thereof(e.g., glasses with no optical correction, glasses optically correctedfor the user, sunglasses, or some combination thereof) based oninstructions from application engine 255.

Display device 205 includes electronic display 215, one or moreprocessors 216, eye tracking module 217, adjustment module 218, one ormore locators 220, one or more position sensors 225, one or moreposition cameras 222, memory 228, inertial measurement unit (IMU) 230,timer 257, thermometer 259, liquid crystal (LC) element controller 258,or a subset or superset thereof (e.g., display device 205 withelectronic display 215, one or more processors 216, and memory 228,without any other listed components). Some embodiments of display device205 have different modules than those described here. Similarly, thefunctions can be distributed among the modules in a different mannerthan is described here.

One or more processors 216 (e.g., processing units or cores) executeinstructions stored in memory 228. Memory 228 includes high-speed randomaccess memory, such as DRAM, SRAM, DDR RAM, or other random access solidstate memory devices; and may include non-volatile memory, such as oneor more magnetic disk storage devices, optical disk storage devices,flash memory devices, or other non-volatile solid state storage devices.Memory 228, or alternately the non-volatile memory device(s) withinmemory 228, includes a non-transitory computer readable storage medium.In some embodiments, memory 228 or the computer readable storage mediumof memory 228 stores programs, modules and data structures, and/orinstructions for displaying one or more images on electronic display215.

Electronic display 215 displays images to the user in accordance withdata received from console 210 and/or processor(s) 216. In variousembodiments, electronic display 215 may comprise a single adjustableelectronic display element or multiple adjustable electronic displayselements (e.g., a display for each eye of a user).

In some embodiments, the display element includes one or more lightemission devices and a corresponding emission intensity array. Anemission intensity array is an array of electro-optic pixels,opto-electronic pixels, some other array of devices that dynamicallyadjust the amount of light transmitted by each device, or somecombination thereof. These pixels are placed behind one or more lenses.In some embodiments, the emission intensity array is an array of liquidcrystal based pixels in an LCD (a Liquid Crystal Display). Examples ofthe light emission devices include: an organic light emitting diode, anactive-matrix organic light-emitting diode, a light emitting diode, alaser, a fluorescent light source, some type of device capable of beingplaced in a flexible display, or some combination thereof. The lightemission devices include devices that are capable of generating visiblelight (e.g., red, green, blue, etc.) used for image generation. Theemission intensity array is configured to selectively attenuateindividual light emission devices, groups of light emission devices, orsome combination thereof. Alternatively, when the light emission devicesare configured to selectively attenuate individual emission devicesand/or groups of light emission devices, the display element includes anarray of such light emission devices without a separate emissionintensity array.

One or more lenses direct light from the arrays of light emissiondevices (optionally through the emission intensity arrays) to locationswithin each eyebox and ultimately to the back of the user's retina(s).An eyebox is a region that is occupied by an eye of a user locatedproximate to display device 205 (e.g., a user wearing display device205) for viewing images from display device 205. In some cases, theeyebox is represented as a 10 mm×10 mm square. In some embodiments, theone or more lenses include one or more coatings, such as anti-reflectivecoatings.

In some embodiments, the display element includes an infrared (IR)detector array that detects IR light that is retro-reflected from theretinas of a viewing user, from the surface of the corneas, lenses ofthe eyes, or some combination thereof. The IR detector array includes anIR sensor or a plurality of IR sensors that each correspond to adifferent position of a pupil of the viewing user's eye. In alternateembodiments, other eye tracking systems may also be employed.

Eye tracking module 217 determines locations of each pupil of a user'seyes. In some embodiments, eye tracking module 217 instructs electronicdisplay 215 to illuminate the eyebox with IR light (e.g., via IRemission devices in the display element).

A portion of the emitted IR light will pass through the viewing user'spupil and be retro-reflected from the retina toward the IR detectorarray, which is used for determining the location of the pupil.Alternatively, the reflection off of the surfaces of the eye is alsoused to determine the location of the pupil. The IR detector array scansfor retro-reflection and identifies which IR emission devices are activewhen retro-reflection is detected. Eye tracking module 217 may use atracking lookup table and the identified IR emission devices todetermine the pupil locations for each eye. The tracking lookup tablemaps received signals on the IR detector array to locations(corresponding to pupil locations) in each eyebox. In some embodiments,the tracking lookup table is generated via a calibration procedure(e.g., user looks at various known reference points in an image and eyetracking module 217 maps the locations of the user's pupil while lookingat the reference points to corresponding signals received on the IRtracking array). As mentioned above, in some embodiments, system 200 mayuse other eye tracking systems than the embedded IR one described above.

Adjustment module 218 generates an image frame based on the determinedlocations of the pupils. In some embodiments, this sends a discreteimage to the display that will tile subimages together, thus, a coherentstitched image will appear on the back of the retina. Adjustment module218 adjusts an output (i.e. the generated image frame) of electronicdisplay 215 based on the detected locations of the pupils. Adjustmentmodule 218 instructs portions of electronic display 215 to pass imagelight to the determined locations of the pupils. In some embodiments,adjustment module 218 also instructs the electronic display not to passimage light to positions other than the determined locations of thepupils. Adjustment module 218 may, for example, block and/or stop lightemission devices whose image light falls outside of the determined pupillocations, allow other light emission devices to emit image light thatfalls within the determined pupil locations, translate and/or rotate oneor more display elements, dynamically adjust curvature and/or refractivepower of one or more active lenses in the lens (e.g., microlens) arrays,or some combination thereof.

Optional locators 220 are objects located in specific positions ondisplay device 205 relative to one another and relative to a specificreference point on display device 205. A locator 220 may be a lightemitting diode (LED), a corner cube reflector, a reflective marker, atype of light source that contrasts with an environment in which displaydevice 205 operates, or some combination thereof. In embodiments wherelocators 220 are active (i.e., an LED or other type of light emittingdevice), locators 220 may emit light in the visible band (e.g., about400 nm to 750 nm), in the infrared band (e.g., about 750 nm to 1 mm), inthe ultraviolet band (about 100 nm to 400 nm), some other portion of theelectromagnetic spectrum, or some combination thereof.

In some embodiments, locators 220 are located beneath an outer surfaceof display device 205, which is transparent to the wavelengths of lightemitted or reflected by locators 220 or is thin enough not tosubstantially attenuate the wavelengths of light emitted or reflected bylocators 220. Additionally, in some embodiments, the outer surface orother portions of display device 205 are opaque in the visible band ofwavelengths of light. Thus, locators 220 may emit light in the IR bandunder an outer surface that is transparent in the IR band but opaque inthe visible band.

Inertial Measurement Unit (IMU) 230 is an electronic device thatgenerates calibration data based on measurement signals received fromone or more position sensors 225. Position sensor 225 generates one ormore measurement signals in response to motion of display device 205.Examples of position sensors 225 include: one or more accelerometers,one or more gyroscopes, one or more magnetometers, another suitabletypes of sensors that detect motion, a type of sensor used for errorcorrection of IMU 230, or some combination thereof. Position sensors 225may be located external to IMU 230, internal to IMU 230, or somecombination thereof.

Based on the one or more measurement signals from one or more positionsensors 225, IMU 230 generates first calibration data indicating anestimated position of display device 205 relative to an initial positionof display device 205. For example, position sensors 225 includemultiple accelerometers to measure translational motion (forward/back,up/down, left/right) and multiple gyroscopes to measure rotationalmotion (e.g., pitch, yaw, roll). In some embodiments, IMU 230 samplesthe measurement signals and calculates the estimated position of displaydevice 205 from the sampled data. For example, IMU 230 integrates themeasurement signals received from the accelerometers over time toestimate a velocity vector and integrates the velocity vector over timeto determine an estimated position of a reference point on displaydevice 205. Alternatively, IMU 230 provides the sampled measurementsignals to console 210, which determines the first calibration data. Thereference point is a point that may be used to describe the position ofdisplay device 205. While the reference point may generally be definedas a point in space, in practice the reference point is defined as apoint within display device 205 (e.g., a center of IMU 230).

In some embodiments, IMU 230 receives one or more calibration parametersfrom console 210. As further discussed below, the one or morecalibration parameters are used to maintain tracking of display device205. Based on a received calibration parameter, IMU 230 may adjust oneor more IMU parameters (e.g., sample rate). In some embodiments, certaincalibration parameters cause IMU 230 to update an initial position ofthe reference point so that it corresponds to a next calibrated positionof the reference point. Updating the initial position of the referencepoint as the next calibrated position of the reference point helpsreduce accumulated error associated with the determined estimatedposition. The accumulated error, also referred to as drift error, causesthe estimated position of the reference point to “drift” away from theactual position of the reference point over time.

Timer 257 is configured to measure the duration of certain processes ofdisplay device 205. In some embodiments, timer 257 measures processesinvolved with adaptive liquid lenses included in display device 205,such as those described below with respect to FIGS. 5A-6C. For example,timer 257 measures a duration of stress applied to an adaptive liquidlens. In some embodiments, timer 257 determines an age of an adaptiveliquid lens based on a timestamp indicating the time of manufacture ofthe adaptive liquid lens. Thermometer 259 measures the temperature ofdisplay device 205, or specific components of display device, such aselectronic display 215 and or other components. In some embodiments,thermometer 259 measures the temperature of lenses included in displaydevice 205 (e.g., adaptive liquid lenses described below with respect toFIGS. 5A-6C). LC Element Controller 258 controls LC optical elementsincluded in display device 205, such as those described below withrespect to FIGS. 5B-5C and FIG. 7. In some embodiments, LC elementcontroller 258 applies a spatially variable voltage (V) to liquidcrystal elements to adjust the refractive index of the liquid crystalelements.

Imaging device 235 generates calibration data in accordance withcalibration parameters received from console 210. Calibration dataincludes one or more images showing observed positions of locators 220that are detectable by imaging device 235. In some embodiments, imagingdevice 235 includes one or more still cameras, one or more videocameras, any other device capable of capturing images including one ormore locators 220, or some combination thereof. Additionally, imagingdevice 235 may include one or more filters (e.g., used to increasesignal to noise ratio). Optionally, imaging device 235 is configured todetect light emitted or reflected from locators 220 in a field of viewof imaging device 235. In embodiments where locators 220 include passiveelements (e.g., a retroreflector), imaging device 235 may include alight source that illuminates some or all of locators 220, whichretro-reflect the light towards the light source in imaging device 235.Second calibration data is communicated from imaging device 235 toconsole 210, and imaging device 235 receives one or more calibrationparameters from console 210 to adjust one or more imaging parameters(e.g., focal length, focus, frame rate, ISO, sensor temperature, shutterspeed, aperture, etc.).

Input interface 240 is a device that allows a user to send actionrequests to console 210. An action request is a request to perform aparticular action. For example, an action request may be to start or endan application or to perform a particular action within the application.Input interface 240 may include one or more input devices. Example inputdevices include: a keyboard, a mouse, a game controller, a touchcontroller, data from brain signals, data from other parts of the humanbody, or any other suitable device for receiving action requests andcommunicating the received action requests to console 210. An actionrequest received by input interface 240 is communicated to console 210,which performs an action corresponding to the action request. In someembodiments, input interface 240 may provide haptic feedback to the userin accordance with instructions received from console 210. For example,haptic feedback is provided when an action request is received orconsole 210 may communicate instructions to input interface 240 to causeinput interface 240 to generate haptic feedback when console 210performs an action.

Console 210 provides media to display device 205 for presentation to theuser in accordance with information received from one or more of:imaging device 235, display device 205, and input interface 240. In theexample shown in FIG. 2, console 210 includes application store 245,tracking module 250, and application engine 255. Some embodiments ofconsole 210 have different modules than those described in conjunctionwith FIG. 2. Similarly, the functions further described below may bedistributed among components of console 210 in a different manner thanis described here.

When application store 245 is included in console 210, application store245 stores one or more applications for execution by console 210. Anapplication is a group of instructions, that when executed by aprocessor, is used for generating content for presentation to the user.Content generated by the processor based on an application may be inresponse to inputs received from the user via movement of display device205 or input interface 240. Examples of applications include: gamingapplications, conferencing applications, educational applications, videoplayback application, or other suitable applications.

When tracking module 250 is included in console 210, tracking module 250calibrates system 200 using one or more calibration parameters, and mayadjust one or more calibration parameters to reduce error in thedetermination of the position of display device 205. For example,tracking module 250 adjusts the focus of imaging device 235 to obtain amore accurate position for observed locators on display device 205.Moreover, calibration performed by tracking module 250 also accounts forinformation received from IMU 230. Additionally, if tracking of displaydevice 205 is lost (e.g., imaging device 235 loses line of sight of atleast a threshold number of locators 220), tracking module 250re-calibrates some or all of system 200.

In some embodiments, tracking module 250 tracks movements of displaydevice 205 using second calibration data from imaging device 235. Forexample, tracking module 250 determines positions of a reference pointof display device 205 using observed locators from the secondcalibration data and a model of display device 205. In some embodiments,tracking module 250 also determines positions of a reference point ofdisplay device 205 using position information from the first calibrationdata. Additionally, in some embodiments, tracking module 250 may useportions of the first calibration data, the second calibration data, orsome combination thereof, to predict a future location of display device205. Tracking module 250 provides the estimated or predicted futureposition of display device 205 to application engine 255.

Application engine 255 executes applications within system 200 andreceives position information, acceleration information, velocityinformation, predicted future positions, or some combination thereof ofdisplay device 205 from tracking module 250. Based on the receivedinformation, application engine 255 determines content to provide todisplay device 205 for presentation to the user. For example, if thereceived information indicates that the user has looked to the left,application engine 255 generates content for display device 205 thatmirrors the user's movement in a virtual environment. Additionally,application engine 255 performs an action within an applicationexecuting on console 210 in response to an action request received frominput interface 240 and provides feedback to the user that the actionwas performed. The provided feedback may be visual or audible feedbackvia display device 205 or haptic feedback via input interface 240.

FIG. 3 is an isometric view of display device 300 in accordance withsome embodiments. In some other embodiments, display device 300 is partof some other electronic display (e.g., digital microscope, a mobiledevice, a smartphone, etc.). In some embodiments, display device 300includes light emission device array 310 and one or more lenses 330. Insome embodiments, display device 300 also includes emission intensityarray 322 and IR detector array 324.

Light emission device array 310 emits image light and optional IR lighttoward the viewing user. Light emission device array 310 may be, e.g.,an array of LEDs, an array of microLEDs, an array of OLEDs, or somecombination thereof. Light emission device array 310 includes lightemission devices 320 that emit light in the visible light (andoptionally includes devices that emit light in the IR).

Emission intensity array 322 is configured to selectively attenuatelight emitted from light emission array 310. In some embodiments,emission intensity array 322 is composed of a plurality of liquidcrystal cells or pixels, groups of light emission devices, or somecombination thereof. Each of the liquid crystal cells is, or in someembodiments, groups of liquid crystal cells are, addressable to havespecific levels of attenuation. For example, at a given time, some ofthe liquid crystal cells may be set to no attenuation, while otherliquid crystal cells may be set to maximum attenuation and/or at someintermediate level of attenuation. In this manner emission intensityarray 322 is able to control what portion of the image light emittedfrom light emission device array 310 is passed to the one or more lenses330. In some embodiments, display device 300 uses emission intensityarray 322 to facilitate providing image light to a location of pupil 350of eye 340 of a user and to minimize the amount of image light providedto other areas in the eyebox.

One or more lenses 330 receive the modified image light (e.g.,attenuated light) from emission intensity array 322 (or directly fromemission device array 310), and direct the shifted image light to alocation of pupil 350.

Optional IR detector array 324 detects IR light that has beenretro-reflected from the retina of eye 340, a cornea of eye 340, acrystalline lens of eye 340, or some combination thereof. IR detectorarray 324 includes either a single IR sensor or a plurality of IRsensitive detectors (e.g., photodiodes). In some embodiments, IRdetector array 324 is separate from light emission device array 310. Insome embodiments, IR detector array 324 is integrated into lightemission device array 310.

In some embodiments, light emission device array 310 and emissionintensity array 322 make up a display element. Alternatively, thedisplay element includes light emission device array 310 (e.g., whenlight emission device array 310 includes individually adjustable pixels)without emission intensity array 322. In some embodiments, the displayelement additionally includes the IR array. In some embodiments, inresponse to a determined location of pupil 350, the display elementadjusts the emitted image light such that the light output by thedisplay element is refracted by one or more lenses 330 toward thedetermined location of pupil 350, and not toward other locations in theeyebox.

As explained above, adaptive liquid lenses are desirable candidates asvarifocal optical elements for adjusting the focal distance of lightemitted by displays of head-mounted display devices. However, theadaptive liquid lenses have a number of challenges that limit their use,as will be described below with respect to FIGS. 4A-4C.

FIG. 4A is a schematic illustration of a gravity effect of liquid lensesin accordance with some embodiments. FIG. 4A illustrates three liquidlenses (e.g., droplets 404 a, 404 b and 404 c) made of an opticallytransparent fluid, and disposed on substrate 402 in three differentorientations: on a horizontal surface (droplet 404 a), below ahorizontal surface (droplet 404 b) and in a vertical direction (droplet404 c). As shown in FIG. 4A, gravity force distorts shapes of droplets404 b and 404 c compared to the horizontally oriented droplet 404 a.Droplet 404 c in a vertical direction has a asymmetric distorted shape.Such distortions modify the focal distance and thereby optical power ofa liquid lens, resulting in optical artifacts. In a head-mounted displaydevice, the orientation of the lens is expected to be in a vertical ornearly vertical direction as a user is standing straight and theorientation of the lens varies according to movements of a user.Therefore, a liquid lens of a head-mounted display device is susceptibleto the gravity effect and to optical artifacts caused by the gravityeffect.

In addition to the gravity effect, liquid lenses are susceptible tooptical artifacts caused by a temperature effect. Temperaturefluctuations affect properties of an optical fluid (e.g., volatility,surface tension, and/or density) resulting in changes of volume and/orshape of the liquid lens. This causes changes in a focal distance andthereby optical power of the liquid lens resulting in optical artifacts.

FIG. 4B is a graph illustration of a creep effect in liquid membranelenses in accordance with some embodiments. A membrane lens is describedin further detail below with respect to FIG. 6C. Membrane lenses are atype of adaptive liquid lenses that include a membrane. In someembodiments, membrane lenses change the focal distance by changing ashape (e.g., curvature or area) of the membrane. For example, themembrane shape can be changed from flat to curved, or from concave toconvex. Also, the curvature of a lens (e.g., a concave lens) can bechanged to provide a different focal distance. The membrane is typicallymade of an elastomeric material, such as a polymer or a silicone. Suchmaterials are susceptible to a creep effect. As used herein, a creepeffect refers to a tendency of a material to alter its response (i.e.,strain) under influence of a mechanical stress over time. The left sidegraph of FIG. 4B illustrates a constant mechanical stress applied on amembrane of a membrane lens. For example, such constant stress maycorrespond to a mechanical stress required for a concave membrane tochange its curvature. The right side graph of FIG. 4B illustrates anexample of strain under an influence of a constant stress where thestrain in response to the constant stress varies over time. For example,applying mechanical stress A on a membrane at time t₁ results in strainB₁ of the membrane causing the membrane to stretch a certain amount(e.g., a concave membrane with a first curvature stretches to a concavemembrane with a second curvature). Applying the same mechanical stress Aon the membrane at time t₂ results in strain B₂ of the membrane. At timet₂, the membrane stretches more (i.e., the concave membrane with thefirst curvature stretches to a concave membrane with a third curvature).In some cases, the membrane tension can initially increase and thendecrease over time. Over time, the varying response to mechanical stressaffects the optical power of the lens and results in optical artifacts.Another effect of the mechanical stress on the membrane is beamdistortions at the edge of the optical aperture of the lens affectingoptical performance.

The gravity effect, thermal effect and creep effect described hereinhave an impact on the overall image quality provided by an adaptiveliquid lens. These effects and/or other deficiencies causing opticalartifacts by a liquid adaptive lens are eliminated or reduced by theembodiments of a hybrid adaptive lens described below with respect toFIGS. 5A-5C.

FIG. 5A is a schematic illustration of adaptive liquid lens 502 inaccordance with some embodiments. Adaptive liquid lens 502 defines arange of focal distances between focal distances f₁ and f₂, and isconfigured to modify the focal distance within that range. FIG. 5A showslight 506 focused by lens 502 at focal distance f₁ and focal distancef₂. Adaptive liquid lenses used for hybrid adaptive lenses are furtherdescribed below with respect to FIGS. 6A-6C. Light 506 has wave-front504-1 when focused at focal distance f₁ and wave-front 504-2 whenfocused at focal distance f₂. Wave-fronts 504-1 and 504-2 are distorted.In some embodiments, wave-fronts 504-1 and 504-2 are distorted due toone or more of the effects described above with respect to FIGS. 4A-4B(i.e., the gravity effect, thermal effect, and/or creep effect). Suchdistorted wave-fronts are observed as optical artifacts in an image.

FIG. 5B is a schematic illustration of hybrid adaptive lens 510 inaccordance with some embodiments. In some embodiments, hybrid adaptivelens 510 corresponds to lens 330 described above with respect to FIG. 3.Hybrid adaptive lens 510 includes adaptive liquid lens 502 and liquidcrystal (LC) optical element 512. In some embodiments, LC opticalelement 512 includes one or more wave-front correctors to correct forwave-front distortions shown by wave-fronts 504-1 and 504-2 of FIG. 5A.In FIG. 5B, wave-fronts 514-1 and 514-2 at respective focal distances f₁and f₂ are corrected by LC optical element 512 to have smooth, sphericalwave-front shapes. The wave-front correction is achieved by dynamicallyadjusting a spatially variable refractive index across LC opticalelement 512. The spatially variable refractive index compensates forspatial distortions of the wave-front. The functionality of a wave-frontcorrector is further described below with respect to FIG. 7.

FIG. 5C is a schematic illustration of hybrid adaptive lens 520 inaccordance with some embodiments. Hybrid adaptive lens 520 correspondsto lens 510 described above with respect to FIG. 5B, except that LCelement 512 includes wave-front corrector 512-1 and LC lens 512-2. Insome embodiments, LC lens 512-2 is an adaptive LC lens. In someembodiments, LC lens 512-2 is composed of one or more layers of liquidcrystals. In some embodiments, LC lens 512-2 adds to the optical powerof hybrid adaptive lens 520 and increases and/or shifts the range offocal distances defined by adaptive liquid lens 502. In FIG. 5C, LC lens512-2 shifts the focal distance range of adaptive liquid lens 502 sothat focal distance f₁ is shifted to focal distance f₃ and focaldistance f₂ is shifted to focal distance f₄, where focal distances f₃and f₄ are shorter than the corresponding focal distances f₁ and f₂ ofadaptive liquid lens 502 in FIG. 5A. Focal distances f₁ and f₂ areillustrated in FIG. 5D with dash lines for reference. Alternatively, LClens 512-2 shifts the focal distance range so that focal distances f₃and f₁ are longer than the corresponding focal distances f₁ and f₂ ofadaptive liquid lens 502. In some embodiments, LC lens 512-2 expands therange of focal distances of adaptive liquid lens 502, so that focaldistance f₃ is shorter than corresponding focal distance f₁ and focaldistance f₄ is longer than the corresponding focal distance f₂.

FIG. 6A is a schematic illustration of adaptive liquid lens 600 inaccordance with some embodiments. Adaptive liquid lens 600 correspondsto adaptive liquid lens 502 of hybrid adaptive lens 510 described abovewith respect to FIGS. 5A-5C. Adaptive liquid lens 600 includes a dropletof an optically transparent fluid (e.g., droplet 604-1, 604-2, or 604-3)positioned on substrate 602. The focal distance of lens 600 isadjustable by adjusting a shape and/or volume of the droplet. Droplet604-1 has a first shape corresponding to a first optical distance (e.g.,focal distance f₁ in FIG. 5B). Droplet 604-2 has a second shapecorresponding to a second optical length (e.g., focal distance f₂ inFIG. 5B). Droplet 604-3 has a third shape corresponding to a thirdoptical length. In some embodiments, adaptive liquid lens 600 is anadaptive membrane lens, a dielectrophoretic, an electrowetting lens, amechanical-wetting lens, a ferrofluidic transducer lens, hydrogel lens,electromagnetic actuator lens, electrochemical actuation lens,electrostatic force actuation lens, an acoustic liquid lens, or adaptiveliquid lens of any other type.

FIG. 6B is a schematic illustration of dielectrophoretic lens 610 inaccordance with some embodiments. Dielectrophoretic lens 610 correspondsto adaptive liquid lens 600 described above with respect to FIG. 6A. Theadaptive functionality of a dielectrophoretic lens is based ondielectrophoresis. Dielectrophoresis refers to a phenomenon of placing aneutral dielectric particle in a spatially non-homogenous electricfield. As a result of the non-homogenous electric field, the dielectricparticle bears a dielectrophoretic force. In a dielectrophoretic lens, aforce is exerted between a liquid droplet (e.g., droplet 614 of adielectric fluid) and a surrounding medium (e.g., medium 608) where theliquid droplet and the surrounding medium have largely differentdielectric constants and different refractive indexes. Thedielectrophoretic force F is described by the following equation:

$\begin{matrix}{{F = {\frac{1}{2}{ɛ_{0}\left( {ɛ_{d} - ɛ_{m}} \right)}{\nabla E^{2}}}},} & (1)\end{matrix}$wherein ε₀ represents vacuum permittivity, ε_(d) is a dielectricconstant of a droplet, ε_(m) is a dielectric constant of a surroundingmedium, and ∇E is an electric field gradient.

Dielectrophoretic lens 610 includes an enclosure formed by substrates602-1 and 602-2 separated by spacers 612-1 and 612-2. In someembodiments, substrates 602-1 and 602-2 are made of glass. Substrate602-1 includes surface 606-1 including an electrode (e.g., an indium tinoxide (ITO) electrode) and a dielectric layer coated on top of theelectrode. Substrate 602-2 includes surface 606-2 facing surface 606-1.Surface 606-2 also includes an electrode (e.g., an ITO electrode).Electrodes on surfaces 606-1 and 606-2 are electronically coupled. Oneor more droplets 614 of an optical fluid are deposited on substrate602-1, and surrounded by surrounding liquid 608. Droplet 614 andsurrounding liquid 608 are composed of an optically clear, immiscibleliquid with matching densities. However, droplet 614 is composed of aliquid that has a largely different dielectric constant and a distinctrefractive index than surrounding liquid 608. The focal distance of lens610 is changed by modifying the shape of droplet 614, similarly to asillustrated by droplets 604-1, 604-2, and 604-3 in FIG. 6A, by applyinga voltage (V) between electrodes of surfaces 606-1 and 606-2 to create aspatially non-homogenous electric field. In some embodiments, two ormore droplets 614 form a single droplet as voltage (V) is applied.

FIGS. 6C-6D are schematic illustrations of membrane lens 620 inaccordance with some embodiments. In some embodiments, membrane lens 620corresponds to adaptive liquid lens 600 described above with respect toFIG. 6A. Adaptive liquid lens 620 includes optically transparent fluid(e.g., fluids 624-1 and 624-2) positioned on substrate 602 encapsulatedby membrane 626 and edge seal 629. Membrane 626 is made of anelastomeric material (e.g., membrane 626 is made of silicone orpolymer). Membrane 626 defines the shape and/or volume of the opticalfluid. In some embodiments, membrane 626 defines a flat shape (e.g.,membrane 626 is flat in FIG. 6C), convex shape (e.g., membrane 626 has aconvex shape in FIG. 6D), or concave shape. The focal distance ofadaptive liquid lens 620 is configured to be adjusted by modifying theshape and/or volume of the fluid (e.g., fluids 624-1 and 624-2)encapsulated by membrane 626 and edge seal 629. Fluid 624-1 in FIG. 6Cand fluid 624-2 in FIG. 6D have different shapes corresponding todifferent focal distances. In some embodiments, liquid lens 620 iscoupled with a fluid reservoir for adjustment of a volume. In someembodiments, the shape and/or volume of the fluid is adjusted by driver628. In some embodiments, driver 628 includes, or is coupled with,actuation mechanisms (e.g., by a syringe, a motor pump, piezoelectricpumping, artificial muscle, a voice coil motor, or any combinationthereof). The adjusting of the shape and/or volume causes stress tomembrane 626 and therefore, over time, results in optical artifactsarising from a creep effect described above with respect to FIG. 4B.

FIG. 7 is a schematic illustration of liquid crystal (LC) wave-frontcorrector 700 in accordance with some embodiments. In some embodiments,wave-front corrector 700 is included in LC element 512 described abovewith respect to FIG. 5B and corrects for the wave-front distortionscaused by adaptive liquid lens 502 due to one or more of the effectsdescribed above with respect to FIGS. 4A-4B (i.e., the gravity effect,the thermal effect and/or creep effect) and/or other distortions. FIG. 7illustrates wave-front corrector 700 before (left side) and after (rightside) applying a voltage (V). Wave-front corrector 700 includes an arrayof LC cells (e.g., cells 702-1, 702-2, 702-3, and 702-4). In someembodiments, each LC cell 702-1, 702-2, 702-3, and 702-4 corresponds toa pixel. In some embodiments, each LC cell 702-1, 702-2, 702-3, and702-4 correspond to a subpixel. In some embodiments, LC cells 702-1,702-2, 702-3, and 702-4 are separate cells. In some embodiments, LCcells 702-1, 702-2, 702-3, and 702-4 are portions of a continuous LCelement. LC cells 702-1, 702-2, 702-3, and 702-4 each include arespective plurality of liquid crystals (LCs) 704-1, 704-2, 704-3, and704-4 oriented vertically in wave-front corrector 700 on the left sideof FIG. 7. The refractive index of an LC element depends on theorientation of the LCs. The refractive index of wave-front corrector 700is configured to be adjusted cell by cell. Such a spatially adjustablerefractive index is used to compensate and/or correct for distortions ofa wave-front locally. In FIG. 7, all LC cells 702-1, 702-2, 702-3, and702-4 have LCs with same orientation corresponding to the samerefractive index (e.g., refractive index n₁). By applying a spatiallyvariable voltage V, the orientation of LCs 704-1, 704-2, 704-3, and704-4 in each respective element can be modified. In FIG. 7, LCs 704-1are oriented horizontally resulting in a second refractive index (e.g.,refractive index n₂) and LCs 704-2 are oriented in a 40 degree angle,resulting in a third refractive index (e.g., refractive index n₃). Thespatially variable voltage (V) does not change the orientation of LCs incells 702-3 and 702-4, and therefore, as a result of the appliedspatially variable voltage, wave-front corrector 700 includes cell 702-1with refractive index n₂, cell 702-2 with refractive index n₃, and cells702-3 and 702-4 with refractive index n₁.

With the principles explained with respect to FIG. 7, a wave-frontcorrector (e.g., wave-front corrector 700) included in LC element 512 ofFIG. 5B corrects for wave-front distortions (e.g., wave-fronts 504-1 and504-2 of FIG. 5A are corrected as wave-fronts 514-1 and 514-2 in FIG.5B). The wave-front correction is controlled by a spatially variablevoltage applied across LC element 512. The voltage applied is selectedaccording to the correction required.

In some embodiments, prior to applying a voltage to the wave-frontcorrector, the wave-front of light 506 transmitted through adaptiveliquid lens 502 is characterized with a wave-front sensor (e.g., aShack-Hartmann wave-front sensor), and a spatially variable voltage isapplied to correct for any distortions in the wave-front detected by thesensor accordingly. Furthermore, the correction can be confirmed by thewave-front sensor by characterizing the wave-front of light 506 afterwave-front correction.

In some embodiments, wave-front distortions due to a gravity effect arecorrected by determining an orientation of hybrid adaptive lens 510 andselecting the spatially variable voltage in accordance with thedetermined orientation. The orientation of hybrid adaptive lens 510,coupled with a head-mounted display device (e.g., head-mounted displaydevice 100 shown in FIG. 1), is determined with position sensors 225and/or IMU 230 described above with respect to FIG. 2. For example,position sensor 225 generates one or more measurement signals inresponse to motion of display device 205 and based on calibration dataof IMU 230, it is determined that hybrid adaptive lens 510, along withdisplay device 205, is in a tilted orientation. Based on an angle of thetilt, the gravity effect on adaptive liquid lens 502 of hybrid adaptivelens 510 is determined (e.g., based on previously collected data), andthe required wave-front correction is defined. A spatially variablevoltage is applied to wave-front corrector 700 of LC element 512accordingly.

Wave-front distortions due to a temperature effect are corrected bydetermining the temperature of hybrid adaptive lens 510, and selectingthe spatially variable voltage in accordance with the determinedtemperature. The temperature is determined by thermometer 259 describedabove with respect to FIG. 2. For example, thermometer 259 detects thatthe temperature of hybrid adaptive lens 510 has increased by a certainamount. The effect of the temperature increase on adaptive liquid lens502 of hybrid adaptive lens 510 is determined (e.g., based on previouslycollected data), and the required wave-front correction is defined. Aspatially variable voltage is applied to wave-front corrector 700 of LCelement 512 accordingly.

Wave-front distortions due to a creep effect are corrected bydetermining a duration that adaptive liquid lens 502 (e.g., membraneliquid lens 620 described in FIG. 6C) has been exposed to a mechanicalstress. The elastomeric membrane (e.g., membrane 626) of membrane lens620 is mechanically stretched to different shapes, such as to shapesillustrated in FIG. 6C. For example, the shape of droplet 604-1corresponds to a shape of membrane 626 without exposing the membrane toa mechanical stress, whereas shapes of droplets 604-2 and 604-3correspond to shapes of membrane 626 when exposed to a mechanicalstress. The duration of applying a mechanical stress can be measuredand/or determined by timer 257 described above with respect to FIG. 2.The creep effect on adaptive liquid lens 502 is determined based on theduration, and optionally based on the amount of stress applied (e.g.,based on previously collected data), and the required wave-frontcorrection is defined. A spatially variable voltage is applied towave-front corrector 700 of LC element 512 accordingly.

In some embodiments, the wave-front distortions due to the creep effectare corrected by determining an age of adaptive liquid lens 502, andadjusting the liquid crystal element based on the determined age. Insome embodiments, the age of adaptive liquid lens 502 is determinedbased on a timestamp indicating a time of manufacture of adaptive liquidlens 502.

In light of these principles, we now turn to certain embodiments.

In accordance with some embodiments, a method includes adjusting a focallength of an adaptive liquid lens that includes a layer of optical fluidon a substrate and in conjunction with adjusting the focal length of theadaptive liquid lens, adjusting a liquid crystal element coupled withthe adaptive liquid lens. In some embodiments, adjusting a liquidcrystal element coupled with the adaptive liquid lens is for reducingoptical artifacts caused by the adaptive liquid lens. For example,hybrid adaptive lens 510 includes adaptive liquid lens 502 and liquidcrystal (LC) element 512 coupled with adaptive liquid lens 502 in FIG.5B. A focal length of adaptive liquid lens 502 is adjusted between focaldistances f₁ and f₂. In conjunction with adjusting the focal length ofadaptive liquid lens 502, LC element 512 is adjusted to reduce opticalartifacts caused by adaptive liquid lens 502. The method also includestransmitting light through the adaptive liquid lens and the liquidcrystal element. For example, hybrid adaptive lens 510 transmits throughlight 506.

In some embodiments, the adaptive liquid lens is a liquid membrane lensor a dielectrophoretic liquid lens (e.g., adaptive liquid lens 502 inFIG. 5B is membrane lens 620 described in FIG. 6C or dielectrophoreticlens 610 described in FIG. 6B).

In some embodiments, adjusting the focal length of the adaptive liquidlens includes changing a shape of the layer of the optical fluid on thesubstrate. For example, adaptive liquid lens 600 adjusts a focal lengthby changing a shape of the optical fluid (e.g., droplets 604-1, 604-2,and 604-3 have different shapes) deposited on substrate 602 in FIG. 6A.In some embodiments, the focal length of the adaptive liquid lensincludes changing a volume of the layer of the optical fluid of thesubstrate (e.g., changing a volume of droplet 604-1).

In some embodiments, the adaptive liquid lens includes a membrane thatat least partially encapsulates the layer of optical fluid, and theshape of the layer of the optical fluid is changed by changing thecurvature of the membrane. For example, membrane lens 620 includesoptically transparent fluid (e.g., fluids 624-1 and 624-2) encapsulatedby membrane 626 and edge seal 629 in FIGS. 6C and 6D. In FIG. 6Cmembrane 626 has a flat shape and in FIG. 6D membrane 626 has a convexshape.

In some embodiments, the layer of the optical fluid includes adielectric liquid material, and adjusting the focal length of theadaptive liquid lens includes applying an electric field to the adaptiveliquid lens. For example, dielectrophoretic lens 610 includes droplet614 of a dielectric optical fluid in FIG. 6B. The focal length ofdielectrophoretic lens 610 is adjusted by applying a spatiallynon-uniform electric field to droplet 614.

In some embodiments, adjusting the liquid crystal element includesadjusting an index of refraction of the liquid crystal element (e.g.,adjusting an index of refraction of LC element 512 of hybrid adaptivelens 510 in FIG. 5B).

In some embodiments, the liquid crystal element includes a wave-frontcorrector, and adjusting the liquid crystal element includes adjustingthe wave-front corrector to reduce optical artifacts arising fromwave-front distortions of the adaptive liquid lens. For example, LCelement 512 of hybrid adaptive lens 520 includes wave-front corrector512-1, which is adjusted to reduce optical artifacts (e.g., opticalartifacts arising from non-uniform wave-fronts 504-1 and 504-2 in FIG.5A are corrected by LC element 512 in FIG. 5B).

In some embodiments, the liquid crystal element includes a liquidcrystal lens, and adjusting the liquid crystal element includesmodifying a focal length of the liquid crystal lens (e.g., hybridadaptive lens 520 includes LC lens 512-2, which is adjusted to modify afocal length).

In some embodiments, adjusting the liquid crystal element includes:determining a temperature of the adaptive liquid lens, and in accordancewith determining the temperature of the adaptive liquid lens, adjustingthe liquid crystal element based on the determined temperature of theadaptive liquid lens. For example, the temperature of adaptive liquidlens 502 in FIG. 5B is determined (e.g., by thermometer 259 in FIG. 2).LC element 512 is adjusted based on the determined temperature to reduceoptical artifacts of adaptive liquid lens 502 caused by a temperatureeffect.

In some embodiments, adjusting the liquid crystal element includesdetermining an orientation of the adaptive liquid lens, and inaccordance with determining the orientation of the adaptive liquid lens,adjusting the liquid crystal element based on the determined orientationof the adaptive liquid lens. For example, an orientation of adaptiveliquid lens 502 in FIG. 5B is determined (e.g., by IMU 230 and positionsensors 225 in FIG. 2). LC element 512 is adjusted based on thedetermined orientation to reduce optical artifacts of adaptive liquidlens 502 caused by a gravity effect.

In some embodiments, determining a duration of exposing the adaptiveliquid lens to a mechanical stress, and in accordance with determiningthe duration of exposing the adaptive liquid lens to a mechanicalstress, adjusting the liquid crystal element based on the determinedduration. For example, timer 257 determines a duration of exposingmembrane lens 620 to a mechanical stress to stretch or shrink membrane626 of membrane lens 620 in FIG. 6C. LC element 512 is adjusted based onthe determined duration to reduce optical artifacts of adaptive liquidlens 502 caused by a creep effect.

In some embodiments, adjusting the liquid crystal element (e.g., LCelement 512 in FIG. 5B) includes determining an age of the adaptiveliquid lens (e.g., lens 502), and adjusting the liquid crystal elementbased on the determined age. In some embodiments, the age of theadaptive liquid lens is determined based on a timestamp indicating atime of manufacture of the adaptive liquid lens.

In accordance with some embodiments, a hybrid lens includes an adaptiveliquid lens and a liquid crystal element coupled with the adaptiveliquid lens. In some embodiments, the liquid crystal element reducesoptical artifacts caused by the adaptive liquid lens. For example,hybrid adaptive lens 510 includes adaptive liquid lens 502 and LCelement 512 coupled with adaptive liquid lens 502 in FIG. 5B. LC element512 reduces optical artifacts caused by adaptive liquid lens 510. Theadaptive liquid lens includes a layer of optical fluid on a substrate(e.g., adaptive liquid lens 600 includes droplet 604-1 on substrate602). A focal length of the adaptive liquid lens is adjustable (e.g.,the focal length of adaptive liquid lens 600 is adjusted by changing theshape of the droplet 604-1 to shapes of 604-2 or 604-3). In someembodiments, the adaptive liquid lens has a diameter of at least 4 cm(e.g., adaptive liquid lens 502 has a diameter of at least 4 cm in FIG.5B).

In some embodiments, the adaptive liquid lens is a liquid membrane lensor a dielectrophoretic liquid lens (e.g., membrane lens 620 ordielectrophoretic lens 610 in FIGS. 6B and 6A, respectively).

In some embodiments, the liquid crystal element includes a liquidcrystal wave-front corrector configured to reduce optical artifactsarising from wave-front distortions of the adaptive liquid lens (e.g.,LC element 512 includes wave-front corrector 512-1 in FIG. 5B).

In some embodiments, the liquid crystal wave-front corrector includes anarray of liquid crystal cells (e.g., LC wave-front corrector 700includes LC cells 702-1, 702-2, 702-3, and 702-4 in FIG. 7).

In some embodiments, the liquid crystal element includes a liquidcrystal lens (e.g., LC lens 512-2 in FIG. 5C). In some embodiments, theadaptive liquid lens defines a range of focal distances, wherein theadaptive liquid lens is configured to modify the focal distance withinthe range of focal distances. For example, LC lens 512-2 modifies focaldistances f₁ and f₂ of adaptive hybrid lens 502 to focal distances f₃and f₄, respectively, so that focal distance f₃ is shorter than focaldistance f₁ and focal distance f₄ is shorter than f₂. Alternatively, LClens 512-2 modifies focal distances f₁ and f₂ of adaptive hybrid lens502 so that the respective modified focal distances are longer thanfocal distances f₁ and f₂.

In accordance with some embodiments, a head-mounted display deviceincludes a hybrid lens described herein (e.g., head-mounted displaydevice 100 in FIG. 1 includes hybrid adaptive lens 510 in FIG. 5B).

In some embodiments, the head-mounted display device further includes atemperature sensor configured to determine a temperature (e.g.,thermometer 259 in FIG. 2), and one or more controllers configured toadjust the liquid crystal element based on the determined temperature(e.g., LC element controller 258 in FIG. 2 is configured to adjust LCelement 512 in FIG. 5B).

In some embodiments, the head-mounted display device further includes anorientation sensor configured to determine an orientation of theadaptive liquid lens (e.g., position sensors 225 with IMU 230 in FIG.2), and one or more controllers configured to adjust the liquid crystalelement based on the determined orientation (e.g., LC element controller258 in FIG. 2 is configured to adjust LC element 512 in FIG. 5B).

In some embodiments, the head-mounted display device further includes atimer configured to indicate a duration of exposing the adaptive liquidlens to a mechanical stress (e.g., timer 257 in FIG. 2), and one or morecontrollers configured to adjust the liquid crystal element based on thedetermined duration (e.g., LC element controller 258 in FIG. 2 isconfigured to adjust LC element 512 in FIG. 5B).

Although some of various drawings illustrate a number of logical stagesin a particular order, stages which are not order dependent may bereordered and other stages may be combined or broken out. While somereordering or other groupings are specifically mentioned, others will beapparent to those of ordinary skill in the art, so the ordering andgroupings presented herein are not an exhaustive list of alternatives.Moreover, it should be recognized that the stages could be implementedin hardware, firmware, software or any combination thereof.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the scope of the claims to the precise forms disclosed. Manymodifications and variations are possible in view of the aboveteachings. The embodiments were chosen in order to best explain theprinciples underlying the claims and their practical applications, tothereby enable others skilled in the art to best use the embodimentswith various modifications as are suited to the particular usescontemplated.

What is claimed is:
 1. A hybrid lens, comprising: a transmissiveadaptive liquid lens that includes a layer of optical fluid on asubstrate, wherein a focal length of the adaptive liquid lens isadjustable; and an optical element including liquid crystals, opticallycoupled with the adaptive liquid lens, configured to adjust a refractiveindex across the optical element including liquid crystals inconjunction with adjusting the focal length of the adaptive liquid lensso that the optical element reduces optical artifacts caused by theadaptive liquid lens, wherein the adaptive liquid lens is a liquidmembrane lens or a dielectrophoretic liquid lens.
 2. The hybrid lens ofclaim 1 wherein the layer of the optical fluid includes a dielectricliquid material, and adjusting the focal length of the adaptive liquidlens includes applying an electric field to the adaptive liquid lens. 3.The hybrid lens of claim 1 wherein: the optical element including liquidcrystals includes a first portion and a second portion distinct andmutually exclusive from the first portion; and adjusting the refractiveindex across the optical element including liquid crystals includes:applying a first voltage across the first portion of the optical elementincluding liquid crystals for orienting liquid crystals of the firstportion of the optical element including liquid crystals in a firstdirection; and applying a second voltage distinct from the first voltageacross the second portion of the optical element including liquidcrystal for orienting liquid crystals of the second portion of theoptical element including liquid crystals in a second direction distinctfrom the first direction.
 4. The hybrid lens of claim 3, wherein theoptical element including liquid crystals includes an array of liquidcrystal cells and the first portion of the optical element includingliquid crystals corresponds to a first liquid crystal cell of the arrayof liquid crystal cells and the second portion of the optical elementincluding liquid crystals corresponds to a second liquid crystal cell ofthe array of liquid crystal cells.
 5. The hybrid lens of claim 1 furtherincluding a liquid crystal lens optically coupled with the opticalelement including liquid crystals, wherein a focal length of the liquidcrystal lens is adjustable.
 6. The hybrid lens of claim 5, wherein theliquid crystal lens is positioned between the adaptive liquid lens andthe optical element including liquid crystals.
 7. The hybrid lens ofclaim 5, wherein the liquid crystal lens is mechanically coupled with,and adjacent to, the optical element including liquid crystals.
 8. Thehybrid lens of claim 5, wherein: the adaptive liquid lens defines afirst range of focal lengths and the focal length of the adaptive liquidlens is adjustable within the first range of focal lengths; and theliquid crystal lens is configured to shift and/or increase or decrease alength of the first range of focal lengths, so that the hybrid lensdefines a second range of focal lengths distinct from the first range offocal lengths.
 9. A hybrid lens, comprising: a transmissive adaptiveliquid lens that includes a layer of optical fluid on a substrate,wherein a focal length of the adaptive liquid lens is adjustable; and anoptical element including liquid crystals, optically coupled with theadaptive liquid lens, configured to adjust a refractive index across theoptical element including liquid crystals in conjunction with adjustingthe focal length of the adaptive liquid lens so that the optical elementreduces optical artifacts caused by the adaptive liquid lens, whereinadjusting the focal length of the adaptive liquid lens includes changinga shape of the layer of the optical fluid on the substrate.
 10. Thehybrid lens of claim 9, wherein the adaptive liquid lens includes amembrane that at least partially encapsulates the layer of opticalfluid, and the shape of the layer of the optical fluid is changed bychanging a curvature of the membrane.
 11. A method, comprising:adjusting a focal length of a hybrid lens, the hybrid lens including atransmissive adaptive liquid lens and an optical element includingliquid crystals optically coupled with the adaptive liquid lens, thetransmissive adaptive liquid lens including a layer of optical fluid ona substrate and having an adjustable focal length, wherein: the adaptiveliquid lens is a liquid membrane lens or a dielectrophoretic liquidlens; adjusting the focal length of the hybrid lens includes: adjustinga focal length of the adaptive liquid lens; and in conjunction withadjusting the focal length of the adaptive liquid lens, adjusting arefractive index across the optical element including liquid crystals sothat the optical element reduces optical artifacts caused by theadaptive liquid lens.
 12. The method of claim 11, wherein: the layer ofthe optical fluid includes a dielectric liquid material; and adjustingthe focal length of the adaptive liquid lens includes applying anelectric field to the adaptive liquid lens.
 13. The method of claim 11,wherein: the optical element including liquid crystals includes a firstportion and a second portion distinct and mutually exclusive from thefirst portion; and adjusting the refractive index across the opticalelement including liquid crystals includes: applying a first voltageacross the first portion of the optical element including liquidcrystals for orienting liquid crystals of the first portion of theoptical element including liquid crystals in a first direction; andapplying a second voltage distinct from the first voltage across thesecond portion of the optical element including liquid crystal fororienting liquid crystals of the second portion of the optical elementincluding liquid crystals in a second direction distinct from the firstdirection.
 14. The method of claim 11, wherein: the hybrid lens furtherincludes a liquid crystal lens, wherein a focal length of the liquidcrystal lens is adjustable; and adjusting the focal length of the hybridlens further includes adjusting the focal length of the liquid crystallens.
 15. The method of claim 14, wherein the liquid crystal lens ismechanically coupled with, and adjacent to, the optical elementincluding liquid crystals.
 16. The method of claim 14, wherein: theadaptive liquid lens defines a first range of focal lengths and thefocal length of the adaptive liquid lens is adjustable within the firstrange of focal lengths; and adjusting the focal length of the hybridlens includes, by adjusting the focal length of the liquid crystal lens,shifting the first range of focal lengths and/or increasing ordecreasing a length of the first range of focal lengths so that thehybrid lens defines a second range of focal lengths distinct from thefirst range of focal lengths.
 17. A method, comprising: adjusting afocal length of a hybrid lens, the hybrid lens including a transmissiveadaptive liquid lens and an optical element including liquid crystalsoptically coupled with the adaptive liquid lens, the transmissiveadaptive liquid lens including a layer of optical fluid on a substrateand having an adjustable focal length, wherein adjusting the focallength of the hybrid lens includes: adjusting a focal length of theadaptive liquid lens, wherein adjusting the focal length of the adaptiveliquid lens includes changing a shape of the layer of the optical fluidon the substrate; and in conjunction with adjusting the focal length ofthe adaptive liquid lens, adjusting a refractive index across theoptical element including liquid crystals so that the optical elementreduces optical artifacts caused by the adaptive liquid lens.
 18. Themethod of claim 17, wherein the adaptive liquid lens includes a membranethat at least partially encapsulates the layer of optical fluid, andchanging the shape of the layer includes changing a curvature of themembrane.